The work, scheduled for completion by year's end, started in June and was wrapped up six weeks ahead of schedule, officials said.

It brings the total to about 3,000 high-resolution security cameras at CTA rail stations, Emanuel said at the CTA Green/Pink Line Clinton station.

The new cameras have already contributed to arrests of 47 suspects robbing and attacking passengers on the CTA system or other crimes against people nearby CTA property in the last five months, officials said.

"The cameras have caught criminals but also serve as a deterrent," Emanuel said.

More than 700 of the new 5000 Series rail cars the CTA is putting into service also are outfitted with cameras. The cameras will eventually provide real-time video feeds to police and the CTA control center, officials said.